Hydraulic pavement breaker



Sept. 29, 1959 s. L. CHRISTENSEN HYDRAULIC PAVEMENT BREAKER 3 Sheets-Sheet 2 Filed Fab. 24, 1958 S m WQQWMW Fig. 2

i M H d She/don L. Christensen INVENTOR. @6161- BY QM 24 MWWEMZEW:

Sept. 29, 1959 s. L. CHRISTENSEN HYDRAULIC PAVEMENT BREAKER 5 Sheets-Sheet 5 Filed Feb. 24, 1958 Fig. 6

She/don L. Christensen 1N VEN TOR. BY W m,,

and

Fig.3

United States Patent iOfiice Patented Sept. 29, 1959 HYDRAULIC PAVEMENT BREAKER Sheldon L. Christensen, Fremont, Nebr. Application February 2 4, 1958, Serial No. 717,013 3 Claims. Cl. 121-25 This invention relates to an impact tool and more particularly to a tool that has a van'ety of uses, both mild and heavy such as as a ground tamper or as a cement breaker.

There are a number of impact tools that are commercially available. Some are constructed especially for milder use, for example to tamp soil or as a post driver. For heavy duty, such as breaking concrete, the lighter tools are not acceptable. An object of this invention is to provide a tool which is smoothly operative as a heavy duty tool but which also functions very well for lighter duty.

An impact tool constructed in accordance with the invention has a main body provided with an anvil and a hammer to strike the anvil. .A sleeve valve is slidable in the cylinder of-the main body and provides means by which the impact tool is cycled. A piston that is on the hammer, is arranged to open and close ports in the sleeve valve and this causes a build up of pressure in the sleeve valve and as a result of this pressure build up, the sleeve valve is adjusted to new positions for each half cycle of operation. The new positions of the sleeve valve register and close intake and return passageways with the ports of the sleeve valve and thereby apply the pressure fluid to the faces of the piston alternately during the operation of the tool.

The travel of the hammer is in a reciprocatory path with the power stroke having the piston and hammer moving down to contact the anvil and this transmits the impact force to the shank which is supported at the lower end of the main body.

This impact tool uses a piston and valve. The piston functions substantially only to shutoff oil flow and permit oil flow by controlling some of the ports in the sleeve valve insofar as valving functions are concerned. The piston is the structure by which the liquid pressure is converted to kinetic energy, but insofar as the valving function of the piston is concerned, it is restricted to the open-' ing and closing of only a few ports. The piston does not capture quantities of the liquid under pressure as do prior pistons in fluid motors of the reciprocatory type. In addition the small force generated by the piston which is used for adjusting the position of the sleeve valve, is mainly taken during the return stroke of the piston thereby leaving the power stroke substantially unaltered as to its force and effectiveness.

Practically all tractors have hydraulic systems with hydraulic power take-off fittings available. Accordingly, the impact tool is constructed to operate from a source of hydraulic fluid under pressure, this fluid ordinarily but not necessarily, being oil. Although tractor powered hydraulic systems are mentioned, itis understood that any other source of hydraulic power that is of sufiicient capacity could be used to power impact tools as disclosed herein.

The simplicity of the tool is important. Complex tools that have many moving parts, are more susceptible to failure, breakdown and improper adjustment than mechanically simplified devices. An impact tool whose principal use is' breaking cement and concrete, cannot be made mechanically complex. Accordingly, it is a further object of the invention to provide a mechanically simplified impact tool that has just a few moving parts and these are uncomplicated in their makeup and in their assembly.

Other objects and features of importance will become apparent in following the description of the illustrated form of the invention.

Figure 1 is of longitudinal sectional view of the impact tool showing the hammer and valve in a position at which the hammer is about to begin its power stroke.

Figure 2 is a longitudinal sectional view of the impact tooland showing the hammer as it has made contact with the anvil and the valve has become adjusted to' a new position that will initiate the return stroke of a single cycle of operation.

Figure 3 is a fragmentary enlarged sectional view showing the passageways and porting of the impact hammer and principally the relationships between them.

- Figure 4 is a transverse sectional view taken on the line 4-4 of Figure 2. showing principally the means for connecting the impact tool to asource and return line in a hydraulic power source.

Figure 5 isa transverse sectional view taken on the line 5-5 of Figure 2 and showing principally the pressure and return passages of the tool.

Figure 6.is a fragmentary sectional view showing principally the pressure and return passageways of the main body.

Figure 7 is a sectional view of the sleeve valve of the tool. Y

Figure 8 is a transverse sectional View taken on the line 88-of Figure 7 and through the upper pressure porting of the sleeve valve.

Figure 9 is an end'view of an insert that constitutes a part of the mainbody of the impact tooland that has ports near one end thereof.

Figure 10'is a sectional view of Figure 9.

Figurell is a sectional view taken on the line l1-11 of Figure 10.

In the accompanying drawings there is an impact tool 10'which exemplifies theprinciples of the invention. This tool is constructed of'a main body 12 having a cylinder 14 extending longitudinally therethrough. Handle 16 is preferably, but not necessarily, provided with grips 18, as at the upper end of the main body 12. A conventional tool shank support 20 is atthe lower end of the body 12 and accommodates and holds shank 22 of a typical tool 24. The tool 24 can have a number of configurations depending on the desires of the user and the material with which the user is working. Anvil 26 is supported in retainer 28 at the lower part of the main body 12. The anvil has a head 30 that is adapted to strike the inner end of shank 22 in order to impart impact forces to the shank. Retainer 28 has a circular passage 32 withtaken on the line 10-7-10 in which anvil 26 is held by packing 34. The anvil can reciprocate but within limits established by the head 30 striking a surface of retainer 28 and the bottom of pocket 36 that is formed in the tool holder 20.

Upper and lower inserts 40 and 42 respectively are fitted in and retained fastened within cylinder 14. Each insert is constructed the same (Figures 9-11). The detailed insert 40 has a cylindrical bore 44 and is in the shape of a sleeve liner. One end of the liner is undercut that forms annular recess 46 with a lower shoulder 48. Recess 46 provides clearance for movement of sleeve valve 50 (Figures 7 and 8) while shoulder 48 has a plurality of grooves 52 in it which terminate in holes 54extending completely through the wall of the insert 40. Insert 40 is applied in cylinder 14 with the recess 46 3 arranged downward when viewed with a tool erect), and the insert 42 is opposite. Accordingly, the recess 46 of insert 40 and the recess 56.01: insert 42 confront each other and are spaced. Sleeve valve 50 is movable upwardly and downwardly in cylinder 14 with the upper and lower ends respectively located always within the confines of recesses 46 and 56.

Sleeve valve 50 has upper and lower portings. The porting can be formed in a number of ways, one :of which is to have a group of slots as at 60 cut into the side wall thereof. There are upper and lower pressure ports 62 and 64 respectively, together with upper .and lower return ports 66 and 68 respectively. The return .ports are located inwardly of the pair of pressure ports 62 and 64 so that they canbe controlled by piston 70-on hammer 72 during parts of the normal .cycle of operation of impact hammer 10. Hammer 72 has piston 70 in its center and the piston is movable in the bore 44 of sleeve valve 40. Circumferential grooves 74 and 76 on opposite sides of the piston faces, and elongate ends 78 and .80 of the piston-hammer are movable in the bores of inserts 40 and 42.

Hydraulic liquid, usually oil, under pressure is taken from any source. The fitting of the pressure line from the source is connected to fitting 82 on the main body 12 and this registers with a bypass passage 84. Fitting 86 on the main body 12 is adapted to connect to the return line of the hydraulic source, and is registered with bypass passage 84. The bypass passage is ordinarily open enabling hydraulic fluid to circulate freely from inlet fitting 82 to the return fitting 86. Manually operated valve 88 closes the bypass passage 84 thereby requiring the hydraulic liquid under pressure to enter the inlet or intake passageway 90 and cause the impact hammer to operate. Valve 80 consists of a valve element 92 that is reciprocable in bore 94, the latter extending transverselyacross bypass passage 84. Spring 96 is seated in bore 94 and applies a yielding bias to the valve element 92 in such direction as to hold the valve elements separated from (open) a blocking position in passage 84. Shank 98 of valve element 92 has its upper end in a wall 100 between the ends of the handle 16. Throttle lever 102 is pivoted in this well and has a part which is generally coextensive with a part of handle 16. When the throttle lever 102 is depressed, valve 88 closes bypass passage 84 requiring the liquid under pressure to enter the inlet passageway 90 that is approximately coextensive with the longitudinal axis of the main body and that is formed in the main body. Passageway 90 has a circular groove 106 registered with it by means of a short recess 108 that communicates passageway 90 with groove 106. Groove 106 and recess 108 constitute a part of the passageway. A similar groove 110 and recess 112 also registers with the elongate part of passageway 90. The two grooves 106 and 110 are formed in the main body 12 and open into its cylinder 14. They are parts of the pressure passageway and are communicated with the pressure ports 62 and 64 respectively of sleeve valve 50. They are opened and closed by the sleeve valve. Return passageway 116 is in main body 12 and is registered with the bypass 84 and return fitting 86 (Figure 4). The return passageway 116 has two circumferential grooves 118 and 120 that are in registry with the elongate part of return passageway 116 by recesses 122 and 124. Grooves 118 and 120 together with recesses 122 and 124 are formed in the main body 12 of the impact tool and open into its cylinder 14. Liquid returning through return passageway 116 can pass through the elongate part of this passageway and flow through branch 128 to enter return fitting 86. There are upper and lower check valves I30 and 132 respectively which are opened in response to pressure for introducing a small quantity of return liquid. Channels 134 and .136 are in registry with the upper and lower parts of the cylinder 14 respectively and these communicate with check valves 130 and 132 for opening them and admitting liquid to their return passageway for recirculation in the power source (unshown).

The operation is described with principal reference to Figures 1 (or 3) and 2. Starting with Figure 1 it is assumed that the valve 88 is closed thereby introducing liquid under pressure into the pressure passageway 90. There is fluid under pressure in the passageway grooves 106 and 110, but groove 'is closed by a part of the sleeve valve 50. Pressure fluid flows through the porting 62 and enters groove 74 of the hammer. Since the projected area of the face of piston 70 confronting groove 74 is greater than the area of the end 78 of the piston, the piston will be moved in a downward direction. This starts the powerstroke of a single cycle of operation. Any liquid that is trapped between the lower face of piston 70 and the upper edge of insert 42 passes into groove of the return passageway 116 because groove 120 is registered with return port 68 and slide valve 50. There is substantially no liquid beneath the hammer end 80 and if there is any small quantity, it will be impressed into the return passageway 116 through channel 136 (Figure 6).

As the hammer approaches and strikes the anvil 26, without having to exhaust any appreciable quantity of oil as is the case in those systems which would have a copious quantity of oil in chamber 140 in advance of the hammer end 80, it delivers the vast majority of the total energy available to the anvil 26. However, in moving down, piston 70 slides down the bore 43 of sleeve valve 50 and occupies a position at which return port 68 is closed. This is very nearly at the end of the power stroke. There is a very small quantity of liquid in advance of the piston 70 when it reaches the position of closing port 68 and this small quantity of liquid being carried in groove 76, enters recess 56 by passing through holes 54 in the insert 42. The result is that the sleeve valve 50 moves up to the position shown in Figure 2 thereby opening pressure port 64 by registering it with pressure passageway groove 110. At the same time return passageway at groove 120 is closed by the sleeve valve and the return passageway is registered with return ports 66 through return passageway groove 118. Accordingly, the piston 70 together with its hammer can and does move upward to start the return stroke. A partial vacuum is drawn in chamber 140 by the return of the piston and this withdraws the liquid from hole 54 and grooves 52 to facilitate a subsequent returning of the sleeve valve 50 to the lowered position. The same action previously took place in connection with the upper recess 46. As the piston returns to the elevated position, the small quantity of oil above the piston from the holes 54, is impressed into the return passageway 116 by entering channel 134 and going through the check valve 130.

When the piston 70 is raised far enough, it closes return port 66 and then with a small further upward movement of the piston, the small quantity of liquid trapped in groove 74, enters the top part of recess 46 and forces the slide valve 50 down to the position shown in Figure 1. Pressure fluid can then enter porting 62 and begin another cycle of operation. The cycle will continue over and over until such time that the user relaxes pressure on throttle lever 102 enabling the normally open valve 88 to return to its normal position bypassing the pressure and return liquid through fittings 82 and 86.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and dcscribed, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.

What is claimed as new is as follows:

1. A hydraulic impact tool comprising a main body having a shank support, said body having a cylinder, an

anvil aligned with said support to strike the shank, a hammer in said cylinder for striking said anvil, a piston movable with said hammer, a sleeve valve having an upper and a lower hydraulic pressure inlet port and an upper and lower return port, pressure and return passageways adapted to be connected to said inlet ports and said return ports respectively during the actuation of said hammer, means including a control valve carried by said body for directing liquid under pressure into said pressure passageway, said sleeve valve axially movably mounted in said cylinder, said upper pressure port registered with said pressure passageway when said hammer is in a raised position so that liquid under pressure may enter said sleeve valve and drive said hammer in a power stroke during which said lower return port is registered with return passageway to exhaust and return most of the liquid in advance of said hammer, said piston closing said lower return port near the end of the power stroke of said hammer to form a pressure build-up in advance of said piston and beneath said sleeve valve thereby moving said sleeve valve upward and open said upper return port and said lower pressure port while closing said upper pressure port and said lower return port.

2. A hydraulic impact tool comprising a main body having a shank support, said body having a cylinder, an anvil aligned with said support to strike the shank, a hammer in said cylinder for striking said anvil, a piston movable with said hammer, a sleeve valve having an upper and a lower hydraulic pressure inlet port and an upper and lower return port, pressure and return passageways adapted to be connected to said inlet ports and said return ports respectively during the actuation of said hammer, means including a control valve carried by said body for directing liquid under pressure into said pressure passageway, said sleeve valve axially movably mounted in said cylinder, said upper pressure port registered with said pressure passageway when said hammer is in a raised position so that liquid under pressure may enter said sleeve valve and drive said hammer in a position stroke during which said lower return port is registered with return passageway to exhaust most of the liquid in advance of said hammer, said piston closing said lower return port near the end of the power stroke of said hammer to form a pressure build-up in advance of said piston and beneath said sleeve valve thereby moving said sleeve valve upward and open said upper return port and said lower pressure port while closing said upper pressure port and said lower return port whereby said hammer moves upward in said sleeve valve and forms a partial vacuum in a part of said cylinder which draws the liquid from behind said sleeve valve and thereby facilitates the return movement of said sleeve valve.

3. The impact tool of claim 2 wherein the main body has a passage registered with the upper part of said cylinder and registered with said return passageway to conduct a portion of the liquid from the upper end of said cylinder into said return passageway in response to the upward movement of said piston, and a check valve in said passage.

References Cited in the file of this patent UNITED STATES PATENTS 

